Many industrial applications require the delivery of large quantities of sand or other granulated or powdered materials in carefully measured quantities. One of the most demanding applications of such a delivery system is the preparation of fracturing fluid commonly used in oil well applications. Sand is the principal ingredient of fracturing fluids and oil well applications require a high volume of fracturing fluids to be continuously pumped into the borehole at high pressures. Very large and metered quantities of sand must be continually delivered to mixing facilities during fracturing applications. Further, the use of fracturing fluids demands careful control of tolerances and density and other parameters that are a function of the sand content.
Delivery and metering devices for fracturing fluid applications also require the monitoring of fracturing fluids in the process of mixing these fluids with the granulated material. The fracturing fluid may include, for example, water, diesel fuel and kerosine. It is desirable to continuously monitor the fracturing fluid level present in the delivery and metering device to ensure that a sufficient amount of fluid is present for the mixing operation. Additionally, it is desired to monitor the fluid level to prevent such fluids from overflowing the delivery and metering device when fluids are not required in the mixing process.
A need has developed for a control system for a delivery and metering device which will ensure the mixing of fracturing fluids having substantially uniform and repeatable characteristics in density and fluid content.